no, it's a known issue, I forgot the circumstances, but rest assured you're not the only one. I usually go back to desktop or whatever window I have open (usually this one) and then go back to DF and it's solved. It usually happened to me when I was accidentally pressing another key but a cursor and shift and suddenly it was moving and moving and unstoppable.
Yeah, when I went back to the game after making the original post, the problem was gone. It happens to me as you describe, but I'm not sure what key it is.
I was thinking maybe Toady had coded in some key combination, e.g. Ctrl+Shift+Arrow to move the screen in the direction of Arrow, and not stop moving until you tell it to, using I don't know what key(s).